@misc{WangWampGibhardtetal., author = {Wang, Mengyi and Wamp, Sabrina and Gibhardt, Johannes and Holland, Gudrun and Schwedt, Inge and Schmidtke, Kai-Uwe and Scheibner, Katrin and Halbedel, Sven and Commichau, Fabian M.}, title = {Adaptation of Listeria monocytogenes to perturbation of c-di-AMP metabolism underpins its role in osmoadaptation and identifies a fosfomycin uptake system}, series = {Environmental microbiology}, volume = {24}, journal = {Environmental microbiology}, number = {9}, issn = {1462-2920}, doi = {10.1111/1462-2920.16084}, pages = {4466 -- 4488}, abstract = {The human pathogen Listeria monocytogenes synthesizes and degrades c-di-AMP using the diadenylate cyclase CdaA and the phosphodiesterases PdeA and PgpH respectively. c-di-AMP is essential because it prevents the uncontrolled uptake of osmolytes. Here, we studied the phenotypes of cdaA, pdeA, pgpH and pdeA pgpH mutants with defects in c-di-AMP metabolism and characterized suppressor mutants restoring their growth defects. The characterization of the pdeA pgpH mutant revealed that the bacteria show growth defects in defined medium, a phenotype that is invariably suppressed by mutations in cdaA. The previously reported growth defect of the cdaA mutant in rich medium is suppressed by mutations that osmotically stabilize the c-di-AMP-free strain. We also found that the cdaA mutant has an increased sensitivity against isoleucine. The isoleucine-dependent growth inhibition of the cdaA mutant is suppressed by codY mutations that likely reduce the DNA-binding activity of encoded CodY variants. Moreover, the characterization of the cdaA suppressor mutants revealed that the Opp oligopeptide transport system is involved in the uptake of the antibiotic fosfomycin. In conclusion, the suppressor analysis corroborates a key function of c-di-AMP in controlling osmolyte homeostasis in L. monocytogenes.}, language = {en} } @misc{CommichauGibhardtHeidemannetal., author = {Commichau, Fabian M. and Gibhardt, Johannes and Heidemann, Jana and Bremenkamp, Rica and Rosenberg, Jonathan and Seifert, Roland and Kaever, Volkhard and Ficner, Ralf}, title = {An extracytoplasmic protein and a moonlighting enzyme modulate synthesis of c-di-AMP in Listeria monocytogenes}, series = {Environmental Microbiology}, volume = {22}, journal = {Environmental Microbiology}, number = {7}, issn = {1462-2920}, doi = {10.1111/1462-2920.15008}, pages = {2771 -- 2791}, abstract = {The second messenger cyclic di-AMP (c-di-AMP) is essential for growth of many bacteria because it controls osmolyte homeostasis. c-di-AMP can regulate the synthesis of potassium uptake systems in some bacteria and it also directly inhibits and activates potassium import and export systems, respectively. Therefore, c-di-AMP production and degradation have to be tightly regulated depending on the environmental osmolarity. The Gram-positive pathogen Listeria monocytogenes relies on the membrane-bound diadenylate cyclase CdaA for c-di-AMP production and degrades the nucleotide with two phosphodiesterases. While the enzymes producing and degrading the dinucleotide have been reasonably well examined, the regulation of c-di-AMP production is not well understood yet. Here we demonstrate that the extracytoplasmic regulator CdaR interacts with CdaA via its transmembrane helix to modulate c-di-AMP production. Moreover, we show that the phosphoglucosamine mutase GlmM forms a complex with CdaA and inhibits the diadenylate cyclase activity in vitro. We also found that GlmM inhibits c-di-AMP production in L. monocytogenes when the bacteria encounter osmotic stress. Thus, GlmM is the major factor controlling the activity of CdaA in vivo. GlmM can be assigned to the class of moonlighting proteins because it is active in metabolism and adjusts the cellular turgor depending on environmental osmolarity.}, language = {en} } @misc{HertelGibhardtMartienssenetal., author = {Hertel, Robert and Gibhardt, Johannes and Martienssen, Marion and Kuhn, Ramona and Commichau, Fabian M.}, title = {Molecular mechanisms underlying glyphosate resistance in bacteria}, series = {Environmental Microbiology}, volume = {23}, journal = {Environmental Microbiology}, number = {6}, issn = {1462-2920}, doi = {10.1111/1462-2920.15534}, pages = {2891 -- 2905}, abstract = {Glyphosate is a nonselective herbicide that kills weeds and other plants competing with crops. Glyphosate specifically inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase, thereby depleting the cell of EPSP serving as a precursor for biosynthesis of aromatic amino acids. Glyphosate is considered to be toxicologically safe for animals and humans. Therefore, it became the most-important herbicide in agriculture. However, its intensive application in agriculture is a serious environmental issue because it may negatively affect the biodiversity. A few years after the discovery of the mode of action of glyphosate, it has been observed that bacteria evolve glyphosate resistance by acquiring mutations in the EPSP synthase gene, rendering the encoded enzyme less sensitive to the herbicide. The identification of glyphosate-resistant EPSP synthase variants paved the way for engineering crops tolerating increased amounts of the herbicide. This review intends to summarize the molecular mechanisms underlying glyphosate resistance in bacteria. Bacteria can evolve glyphosate resistance by (i) reducing glyphosate sensitivity or elevating production of the EPSP synthase, by (ii) degrading or (iii) detoxifying glyphosate and by (iv) decreasing the uptake or increasing the export of the herbicide. The variety of glyphosate resistance mechanisms illustrates the adaptability of bacteria to anthropogenic substances due to genomic alterations.}, language = {en} }